1. Field of the Invention
This invention relates to extraction of useful energy from hot fluids which may contain salts and other dissolved minerals.
It is known that the interior of the earth is a molten mass of rocks and is very hot. This geothermal heat energy may advantageously and efficiently be employed as a primary source of energy for the generation of power through fluid as a carrier. The fluid may appear as steam released from volcanic areas or hot water which is present in volcanic deposits and in deep alluvial deposits that are porous enough to permit percolation of water to the deep hot zones. This fluid may have a temperature as high as 700.degree. F. at a depth of 5,000 feet.
2. Description of the Prior Art
In areas where steam alone is produced, the steam may be used directly in turbines to drive generators to generate electricity. Where there is a mixture of steam and hot water, the steam may be separated in a flash chamber and then used in a steam turbine or to heat a working fluid. However, the steam and the hot water generally contain corrosive materials that can cause destruction of the critical and expensive parts of the rotating machinery employed to convert the energy of the steam and hot water into mechanical and/or electrical energy.
As an efficient way of utilizing hot fluid which may contain salts and other dissolved minerals, especially hot fluids from a geothermal well, a working fluid is superheated by passing the working fluid in heat exchange relationship with the hot fluid. The working fluid has a boiling point that is below the input temperature of the hot fluid. This method and apparatus for utilizing the hot fluid as a primary source of energy represents an efficient way for generating power from hot fluids.
However, there are some hot fluids that contain such a degree of salts and other dissolved minerals that the above method may not be efficiently and economically useful over a long period of time. For example, it is known that the water from some of the geothermal wells in the Imperial Valley in California have more than 400,000 parts per million of dissolved solids which include salts and other minerals. The passage of this brine through a heat exchanger can result in the deposit of silica or other types of scale therein with a substantial decrease in the heat transfer efficiency within the heat exchanger and an increase in the pressure drop through the exchanger.